1. Field of the Invention
The present invention relates to an injection molding machine and particularly to a temperature regulator of a temperature regulating part under a hopper.
2. Description of the Related Art
In an injection molding machine, resin as molding material is charged into a heating cylinder from a hopper, the resin as the molding material is heated and melted by rotation of a screw disposed in the heating cylinder and a heater disposed at an outer periphery of the heating cylinder, and the molten resin is injected into a mold. Because the resin as the molding material is charged into the heated heating cylinder, the resin as the molding material is partially melted in a charging portion from the hopper and the molten resin parts are coupled to each other to form bridges and, as a result, obstructs entrance of the resin into the heating cylinder. To solve this problem, a part under the hopper is conventionally treated as a temperature regulating part under the hopper (water jacket) a temperature of which should be regulated.
For example, there is art in which a radiator is disposed to face a fan of an air-cooling mechanism for an injection motor, a pump circulates cooling water between a temperature regulating part under a hopper and a radiator, the cooling water is heat-exchanged with cold air sent by the fan in the radiator, and the temperature regulating part under the hopper is cooled with the cooling water as disclosed in Japanese Patent Application Laid-open No. 62-284715.
There is also art in which a temperature sensor for detecting a temperature in a heating cylinder and a temperature sensor for detecting a temperature of abase block (a temperature regulating part under a hopper) are provided, a temperature controller sends a water temperature control signal and a water flow rate control signal to a drive unit of a water supplying device based on signals from the two temperature sensors, the drive unit drives a temperature regulator based on the water temperature control signal to adjust a temperature of water circulating among the base block (the temperature regulating part under the hopper), the temperature regulator, and a pump and to control a water flow rate of the pump based on the water flow rate control signal as disclosed in Japanese Patent Application Laid-open No. 2001-179416.
There is a temperature controller including a pump for circulating a cooling medium between a temperature regulating part under a hopper and a cooling medium tank, a heater for heating a cooling medium cooling part and the cooling medium in the tank, and a temperature control unit for detecting a temperature of the cooling medium to perform an ON/OFF control of the heater as disclosed in Japanese Patent Application Laid-open No. 2002-137271.
Moreover, there is a controller which includes a temperature regulator having a heat exchanger, a refrigerant heater, a refrigerant refrigerator, a temperature detector, a refrigerant circulating pump, an industrial water circulating pump, and the like and in which the refrigerant and the industrial water are heat-exchanged with each other by the heat exchanger to control the temperature of the refrigerant at a predetermined temperature to control the temperature of a cylinder flange (temperature regulating part under the hopper) as disclosed in Japanese Patent Application Laid-open No. 2002-172667.
Although the various devices have been developed as a temperature regulator of a temperature regulating part under the hopper as described above, they require a heater or a refrigerator. Moreover, they require the specific controller for controlling the temperature. For example, in the above art described in Japanese Patent Application Laid-open No. 62-284715, temperature control is not carried out. The above art described in Japanese Patent Application Laid-open No. 2001-179416 requires a cooling medium refrigerating portion and a heater and also requires the specific temperature control portion for controlling the temperature. Furthermore, the above art pieces described in Japanese Patent Application Laid-open No. 2002-137271 and Japanese Patent Application Laid-open No. 2002-172667 include the means for heating and cooling the refrigerant and the controller for controlling the means and are expensive.